A conventional transceiver is constructed as shown in FIG. 6 (for example, Japanese Patent Application, First Publication No. Hei 5-7166). FIG. 6 is a block diagram showing an example of the conventional transceiver. A received signal is inputted from an input terminal 61 to a frequency mixer 62, and is converted into an immediate frequency signal according to a signal from a local oscillator 63. The converted immediate frequency signal is inputted through a BPF (band pass filter) 64 to a demodulator 65, is demodulated, and is outputted as a demodulated signal.
Meanwhile, the temperature detector 66 for detecting an ambient temperature of the local oscillator 63 and the BPF 64 outputs a detection signal to a temperature corrector 67. The temperature corrector 67 outputs a predetermined correction control signal to a frequency controller 68 in order to correct variation of a oscillator frequency of the local oscillator 63 corresponding to variation in temperature. The frequency controller 68 controls the oscillator frequency of the local oscillator 63 according to the inputted correction control signal, thus preventing deterioration of the receiving sensitivity due to variation in temperature.
The ambient temperatures of the local oscillator and the BPF are detected and the oscillator frequency of the local oscillator, that is, the local oscillator frequency is corrected based on the detection result. However, the limitation bandwidth (frequency characteristic) of the BPF is varied due to variation of the ambient temperature, thereby causing a problem that the receiving sensitivity deteriorates. Further, because the temperature characteristic is irregular, deterioration of the receiving sensitivity cannot be prevented.